1. D43 Measuring Earthquakes

2. D43 Earthquake Background 1
Earth’s plates are still moving.
The North American plate is moving away from the European plate at 2cm (1in) per year.
Moving these plates takes a lot of energy.
Some of this energy causes large sections of underground rock to break and shift position, resulting in earthquakes (ground shaking).

3. D43 California Earthquakes

4. D43 San Andreas Fault, CA

5. D43 Earthquake Background 2
Scientists measure strength of an earthquake using a tool known as a seismograph.
A seismograph contains a thin needle-like pen that records the movements detected within the Earth on a roll of paper.
The lines on the paper are called seismograms
CHALLENGE QUESTION:
How do seismographs measure earthquakes?

6. D43 Seismograph

7. D43 Seismograms

8. D43 Earthquake Analysis: Date______ Name_____________________ Hr___
Answer in complete paragraphs.
On a separate sheet of paper:
Draw & label a seismograph AND explain how it works in detail using one paragraph.
Draw a seismogram AND explain what it tells in detail using one paragraph.

9. D43 Earthquake Procedure
Set up the seismograph model shown below:
See the model on p D33 in the textbook.
Fold a sheet of plain paper in half, lengthwise. Slide the top of the folded sheet into the clip at the end of the paper tray of Plate B (the larger half of the model). Be careful.
Remove the cap from the marker and insert it point-down into the holder attached to the end of the spring on Plate B.

10. D43 Earthquake Procedure
4. Adjust the marker and the spring so that the marker is pressed firmly enough against the paper to leave a mark, but not so firmly that it can no longer move. Check to see if the marker is positioned properly by gently pulling back the spring and then releasing it. The marker should leave a curved line on the paper.

11. D43 Earthquake Procedure
5. Decide which person will perform each of the following roles in your group. Plate A Holder: hold the handle of Plate A and press down to keep it steady. Plate B Holder: push Plate B directly away from you, just hard enough that Plate B slides past Plate A and the toothpick breaks. Don’t start pushing until the Data Recorder tells you.

12. D43 Earthquake Procedure
5. Data Recorder: Slowly pull string to slide paper tray out of Plate B (leaving a straight marker line on the paper). After the line is 3-5 cm long (1-2 inches), tell Plate B person to start pushing Plate B while you keep slowly pulling the paper tray. You should stop pulling the tray when you almost reach the end of the paper. Observer: observe the movement of each plate and the resulting seismograph.

13. D43 Earthquake Procedure
6. Push the 2 plates together & put a toothpick into the groove formed by the two halves. 7. Simulate an earthquake on a plate boundary by completing your roles as described in Step Discuss your observations of the seismograph model, the seismogram, and the force needed to break the toothpick. Then record your observations for this trial in your lab book.

14. D43 Earthquake Procedure
9. Collect any toothpick pieces left in the groove of either Plate and any that may have fallen onto the table or the floor. Throw these pieces away. 10. Remove the folded paper from the clip and turn it to the blank side. Insert the paper back into the clip with the blank side face up. 11. Keep the same roles and repeat Steps 6-10.

15. D43 Earthquake Procedure
12. Replace the folded paper with a new sheet. Switch the roles among your group members and repeat Steps 6-10 until every member of your group has pushed Plate B two times. 13. Unfold the 4 sheets of paper so that all of the recorded data can be seen at the same time. Compare the 8 seismograms. Discuss your observations with your group.

16. D43 Earthquake Analysis: Date______ Name_____________________ Hr___
Answer using complete paragraphs
What was similar about your 8 seismographs
What was different about the 8 seismographs
What did each half of the seismograph model represent?
What did the toothpick represent?
When did an “earthquake” occur?